Call set-up for fixed wireless communications system

ABSTRACT

A fixed wireless communication system ( 100 ) is a hybrid of a fixed wire-line telephone system and a conventional cellular radio system. In particular, this fixed wireless telephone system ( 100 ) provides an instant communication link between a user&#39;s fixed wireless terminal ( 101 ) and a wire line communication system ( 105 ), allowing a user to dial another user&#39;s number, as well as, receive call progress tones such as the dial tone. This link is established by detecting ( 403 ) an off hook signal at the communication device, transmitting ( 405 ) a call set up request with a “ghost” telephone number over the conventional cellular system, and recognizing ( 411 ) the “ghost” telephone number, requesting ( 413 ), responsive thereto, an audio link on the wire line communication system ( 105 ), and linking ( 415 ) the audio link on the wire line communication system with the first communication device over the conventional cellular radio communication system.

FIELD OF THE INVENTION

Generally, the present invention relates to communication systems andmore particularly to a communication system including a radiocommunication system and a wire line communication system acting as afixed wireless communication system.

BACKGROUND OF THE INVENTION

Generally, a fixed wireless telephone service is used as an alternativeto wire line telephone service in rural or urban settings, particularlyin developing countries. One way of providing a fixed wireless telephoneservice is to use a conventional cellular telephone system and couple itwith a wire line telephone system to provide wireless service to fixedterminals throughout a geographic area.

There are obvious differences between a conventional cellular telephonesystem and a conventional wire line telephone system. For example, in awire line telephone system, upon detection of the off hook condition inthe communication device an audio line is directly coupled between awire line telephone switch and the user's communication device. Thisaudio line provides instant dialing services for the user and providesdial tone feedback to the user indicating service is available. In aconventional cellular system, a phone number is dialled and then anindicator or send button is depressed to transmit a message indicatingto a central base station that a call or communication is desired. Aftera certain amount of delay a communication channel is allocated to theuser and is routed directly to the dialed number. No direct dialing onthe communication channel is allowed and the system does not providedial tone feed back.

In order to provide a fixed wireless telephone service, it is desirableto emulate the service of a fixed wire line telephone service.Specifically, it would be advantageous to provide dial tone feedback andimmediate connection to a telephone switch upon transmitting an off hooksignal from a communication unit in a fixed wireless telephone system.

SUMMARY OF THE INVENTION

A first aspect of the present invention provides a method of call setupfor use in a communication system including a radio communication systemand a wireline communication system, the method comprising the steps ofdetecting an off-hook condition at a first communication device;transmitting, responsive to said step of detecting, a predetermineddigital bit stream using the radio communication system; recognizing thepredetermined digital bit stream as a request for communicationservices; requesting, responsive to said step of recognizing, an audiolink on the wireline communication system; and linking the audio link onthe wireline communication system with the first communication deviceover the radio communication system, thereby forming a communicationlink between the first communication device and the wirelinecommunication system allowing a user to dial a desired communicationnumber.

A second aspect of the present invention provides a call setup apparatusfor use in communication system including a radio communication sytemand a wireline communication system, the call setup apparatuscomprising: a detector for detecting an off-hook signal at a firstcommunication device; a radio transmitter, responsive to said detector,for transmitting a predetermined digital bit stream over the radiocommunication system; a radio receiver for receiving the predetermineddigital bit stream; a controller comprising: means for recognizing thepredetermined digital bit stream as a request for service; means,responsive to the means for recognizing, for requesting an audiolink onthe wireline communication system, and linking the audiolink with thefirst communication device thereby allowing a user to dial a desiredcommunication number.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a fixed wireless telephone serviceincorporating a conventional cellular telephone system and aconventional wire line telephone system in accordance with the presentinvention.

FIG. 2 is a detailed illustration in block diagram form of a base siteinter-connection in accordance with the present invention.

FIG. 3 is an illustration in block diagram form of an enhancement deviceconsole in accordance with the present invention.

FIG. 4 is an illustration in process flow chart form of a call set upmethod in accordance with the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The preferred embodiment includes a description of a fixed wirelesssystem that is a hybrid of a fixed wire-line telephone system and aconventional cellular radio system. It is intended as an alternative towire line telephone system in rural or urban settings, particularly indeveloping countries. A fixed wireless telephone system saves thetremendous cost of providing the infrastructure required for a wire linetelephone system and allows rapid installation of the service. Inparticular, this fixed wireless telephone system provides an instantcommunication link between a user's fixed wireless terminal and a wireline communication system, allowing a user to dial another user'snumber, as well as, receive call progress tones such as the dial tone.This link is established by detecting an off hook signal at thecommunication device, transmitting a call set up request with a “ghost”telephone number over the conventional cellular system, and detectingthe ghost telephone number, requesting, responsive thereto, an audiolink on the wire line communication system, and linking the audio linkon the wire line communication system with the first communicationdevice over the conventional cellular radio communication system. Whenmodifying the conventional cellular system in the above manner, the useris provided with an instant link between the wire line communicationsystem and a communication device in the fixed wireless telephoneservice, thus emulating a traditional wire line communication system.

FIG. 1 is an illustration of a fixed wireless communication system 100including a fixed wireless terminal 101, a fixed wireless base station103 and a conventional wire line switch 105. The fixed wireless terminal(FWT) 101 includes a traditional wire line communication device 107 suchas a modem, a telephone or a fax machine. The fixed wireless terminal101 additionally includes a PSTN interface 109, an enhancement device111 and a cellular radio telephone transceiver 113.

The communication device 107 is any traditional wire line communicationdevice such as a telephone, a fax machine or a modem. The communicationdevice 107 is coupled to the PSTN interface via a traditional two-wireconnection as is known in wire line communication systems. The PSTNinterface 109 provides a traditional interface to a communication devicesuch that the end user is not aware of any difference between a fixedwireless communication system and a fixed wire line communicationsystem. Additionally, the PSTN interface detects traditional signallingcreated by the communication device 107, such as an off hook signal, anon hook signal and a switch hook signal. The PSTN interface 109transmits the analogue audio between the communication device 107 andthe enhancement device 111. Additionally, the PSTN interface 109transmits the detected standard communication device signals (on hook,off hook, switch hook) to the enhancement device 111 and communicatesany standard wire line signals such as an incoming call signal, ametering pulse or an end of call signal from the enhancement device tothe communication device 107.

The enhancement device 111 digitises the audio received from the PSTNinterface 109 and transmits it to a standard cellular radio telephonesystem transceiver 113. Likewise, the audio received from thetransceiver 113 is converted to analogue audio signals. Likewise, theenhancement device 111 converts the digital audio received from thetransceiver 113 to analogue audio and is output to the PSTN interface109. Additionally, the enhancement device 111 provides the necessaryenhancement for operating the traditional cellular transceiver 113 in afixed wireless telephone environment. Specifically, in response toreceiving an original off hook signal from the PSTN interface 109, theenhancement device requests a communication channel on the conventionalcellular radio communication system by transmitting a pre-determineddigital sequence to the transceiver 113. In the preferred embodimentthis predetermined digital sequence is a “ghost” telephone number. Thespecific details of this request are described below. Additionally, theenhancement device 111 codes and decodes traditional wire line signals,such as on hook, off hook, flash hook, metering pulse and end ofcommunication signals.

The transceiver 113 is a standard cellular radio telephone systemtransceiver. In a preferred embodiment, the transceiver is developed tomeet the TACS analogue cellular radio telephone system. However, it isenvisioned that any other traditional cellular radio telephonecommunication system could be substituted therefor including analogueand digital cellular systems. The transceiver 113 transmits and receivesradio frequency “RF” signals to and from a base site transceiver 115located in the fixed wireless base station 103. The base sitetransceiver 115 is comparable with the radio transceiver 113 of thefixed wireless terminal 101. The base site transceiver 115 sends andreceives digital audio signals to and from an enhancement device console117. The enhancement device console 117 contains a plurality ofenhancement devices earlier described in relation to the fixed wirelessterminal 101. Again, the enhancement devices 111 contained in theenhancement device console 117 digitise analogue audio signalstransmitted there to pass those digital audio signals on to the basesite transceiver 115. Likewise, the enhancement devices 111 containedwithin the enhancement device console 117 transform received digitalaudio signals into audio signals for use in the traditional wire linetelephone system. Additionally, the enhancement devices contained withinthe enhancement device console 117 code and decode the signalstransmitted between enhancement device 111 of the fixed wirelessterminal and enhancement devices in the enhancement device console 117.

The channel bank multiplexer (MUX) 119 is coupled to a digital accessinterface (DAI) 121 via an E1 trunk 123. The digital access interface121 may be remotely located from the base site transceiver 115. In thepreferred embodiment, the enhancement device console 117 and the channelbank MUX 119 and are coupled using a microwave link. The channel bankMUX 119 converts audio received from the digital access interface 121into four-way audio which is then transmitted to the enhancement deviceconsole 117. Likewise, four-way audio received from the enhancementdevice console 117 is converted by the channel bank MUX 119 into onetrunk and output to the digital access interface 121.

The digital access interface 121 provides a standard trunk levelinterface such as R2 or SAT, or a proprietary interface to the localcentral office switch. Thus, the DAI 121 interfaces between the E1 trunk123 and the public switching telephone network 105. Additionally, theDAI 121 requests audio links on the wire line communication system andlinks the audio link on the wire line communication system with acommunication channel on the conventional cellular radio telephonesystem, thus providing a link between the communication device 107 andthe PSTN 105.

FIG. 2 is a detailed illustration in block diagram form of a portion ofthe fixed wireless base station 103. Specifically, FIG. 2 includes thebase site transceiver 115, the enhancement device console 117, thechannel bank MUX 119, the E1 interface 123 and the interconnectionsbetween these devices. The base site transceiver 115 includes atransceiver 201 for each of the radio communication channels to a fixedwireless communication device such as FWT 101 of FIG. 1. It should benoted that the number of transceivers necessary will vary depending uponthe cellular system utilised in this communication system 100.Specifically, if a time division multiple access system is used, theneach transceiver could service multiple fixed wireless telephonydevices, thus, reducing the number of required transceivers. Eachtransceiver 201 of the base site transceiver 115 is coupled to theenhancement device console 117 via a four-wire connection 203. Each ofthe transceivers 201 are coupled to an enhancement device 111 containedwithin the enhancement device console 117. In the preferred embodiment,up to 30 transceivers and 30 corresponding enhancement devices may beutilised. Each of the enhancement device 111 transmits a four-wireanalogue audio signal to and from the channel bank MUX 119 via lines205. Additionally, the enhancement devices 111 code and decode the realtime signalling bits which are used to transmit the traditional wireline signals such as on hook, off hook, flash hook, metering pulses andcall termination via the real time signalling connections 207.

FIG. 3 is a detailed illustration in block diagram form of a enhancementdevice 111 of the present invention. The enhancement device includes aDSP 301, a first codec 303, a second codec 305, external memory 307, aninterface connector 309, a first set of filters 311 related to the firstcodec 303 and a second set of filters 313 related to the second codec305. In the preferred embodiment, the DSP 301 is a 16 bit fixed pointDSP operating at 80 megahertz (Mhz). For outgoing audio, the DSP 301receives a string of binary numbers representing an analog audio signal.It converts this string to a digital stream that represents the actualdata or voice recieved from the communication device 107 or from thePSTN 105. It then encodes the voice or data using the first code 303 orthe second codec 305, filters the signals using the appropriate set offilters and transmits the encoded data/voice to the interface connector309. For incoming audio, the DSP 301 performs decodes the data/voicedigital signals, converting them back to an analog audio signal,reversing the outgoing audio process previously described. Additionally,the enhancement device 111, encodes and decodes the traditionaltelephony signals (on hook, off hook, switch hook, metering pulses, calldisconnect) on to and off of the audio signals received by andtransmitted from the enhancement device 111.

FIG. 4 is an illustration in process flow diagram form of a method 400of call setup in accordance with the present invention. The methodstarts at 401. At function block 403, the PSTN interface 109 of FIG. 1detects an off-hook condition at the communication device 107. Atfunction block 405, the enhancement device 111 of FIG. 1 transmits,responsive to said step of detecting, a predetermined bit stream to thetransceiver 113 for transmission on a control channel of the radiocommunication system. In the preferred embodiment, the predetermined bitstream is a “ghost” telephone number, as previously described. Atfunction block 407, the fixed wireless base site 103 receives thepredetermined bit stream. In response to receiving the predetermined bitstream, the fixed wireless base site 103 sets up a traffic channel forcommunication between the fixed wireless base site 103 and thecommunication device 107 at function block 409. The predetermined bitstream is then passed on to the DIA 121 within the fixed wireless basesite 103. At function block 411, the DIA 121 recognises thepredetermined digital bit stream as a request for communicationservices. At function block 413, the DIA 131 requests, responsive tosaid step of recognising, an audio link on the wireline communicationsystem 105 of FIG. 1. The DIA 121 then links the audio link on thewireline communication system with the first communication device overthe radio communication system, at function block 415. The communicationdevice 107 then receives the dial tone from the wireline communicationsystem, at function block 417, as it would in a wireline communicationsystem. The user then dial a dual tone multi-frequency (DTMF) code tothe wireline communication system over the traffic channel of the radiocommunication system, at function block 419. The method 400 ends at 421.

What is claimed is:
 1. A method for setting up a call between a fixedwireless subscriber terminal and a wireline communication network via awireless transceiver, the method comprising the steps of: detecting inthe fixed wireless subscriber terminal an off-hook condition;generating, in the fixed wireless subscriber terminal, responsive tosaid step of detecting, a predetermined telephone number andtransmitting the predetermined telephone number, over a wireless link tosaid wireless transceiver; recognizing, in said wireless transceiver,the predetermined telephone number as a request for communicationservices; requesting in said wireless transceiver, responsive to saidstep of recognizing, an audio link from the wireline communicationnetwork; and, in the wireless transceiver linking the audio link fromthe wireline communication network with the fixed wireless subscriberterminal, forming a communication link therebetween and thereby allowinga subscriber to dial a desired communication number.
 2. The method ofclaim 1 further comprising the step of retransmitting call progresstones and announcements generated by the wireline communication networkto the fixed wireless subscriber terminal.
 3. The method of claim 2wherein the call progress tones include the dial tone.
 4. Apparatus forsetting up a call between a fixed wireless subscriber terminal and awireline communication network via a wireless transceiver, the callsetup apparatus comprising: a detector in the fixed wireless subscriberterminal for detecting an off-hook signal; a radio transmitter in thefixed wireless subscriber terminal, responsive to said detector, fortransmitting a predetermined telephone number over; a wireless link tosaid wireless transceiver; an access device in the wireless transceivercomprising: means for recognizing the predetermined telephone number asa request for service; means, responsive to the means for recognizing,for requesting an audiolink from the wireline communication network, andfor linking the audiolink with the fixed wireless subscriber terminalthereby allowing a subscriber to dial a desired communication number. 5.An apparatus in accordance with claim 4 further comprising a secondtransmitter for retransmitting call progress tones and announcementsgenerated by the wireline communication network to the fixed wirelesssubscriber terminal via the wireless transceiver.
 6. The apparatus ofclaim 5 wherein the call progress tones include the dial tone.
 7. Theapparatus of claim 4 wherein said wireless transceiver forms a part ofan analogue cellular radio communication system.